트리 아이콘 스타일 재정의

<style>
/* 트리 아이콘 재정의 */
.aui-grid-tree-plus-icon {
	display: inline-block;
	width: 16px;
	background: url(./assets/tree_plus.png) 50% 50% no-repeat;
	background-size: 16px;
	margin: 0 4px 2px 0;
}

.aui-grid-tree-minus-icon {
	display: inline-block;
	width: 16px;
	height: 16px;
	background: url(./assets/tree_minus.png) 50% 50% no-repeat;
	background-size: 16px;
	margin: 0 4px 2px 0;
}

.aui-grid-tree-branch-icon {
	display: inline-block;
	width: 16px;
	height: 16px;
	background: url(./assets/tree_branch.png) 50% 50% no-repeat;
	background-size: 16px;
	margin: 0 2px 0 0;
}

.aui-grid-tree-branch-open-icon {
	display: inline-block;
	width: 16px;
	height: 16px;
	background: url(./assets/tree_branch.png) 50% 50% no-repeat;
	background-size: 16px;
	margin: 0 2px 0 0;
}

.aui-grid-tree-leaf-icon {
	display: inline-block;
	width: 16px;
	height: 16px;
	background: url(./assets/tree_leaf.png) 50% 50% no-repeat;
	margin: 0 2px 0 0;
}
</style>